1. Field of the Invention
The invention relates to a transimpedance amplifier circuit including an inverting voltage amplifier having an input which is supplied with an input current and an output that carries an output voltage, and a coupling member that is connected between the input and output of the voltage amplifier.
One such transimpedance amplifier circuit is known, for instance, from the book entitled: Electronic Circuits--Design and Applications, by Ulrich Tietze and Christoph Schenk, Berlin and Heidelberg, 1991, page 97, in which an ohmic resistor is provided as the coupling member. Transimpedance amplifier circuits convert an input current into a proportional voltage, and as a rule are therefore used to amplify the currents generated by photodiodes. That current may be quite small, such as 1 .mu.A, or by comparison quite large, such as 1 mA. That presents dimensioning problems, which can be ascribed in particular to the ohmic resistor that is used in the feedback loop in the known structure.
The resistor must be small in order to avoid overdrive of the transimpedance amplifier circuit when high currents are involved. However, then the input noise of the transimpedance amplifier circuit rises, since smaller resistors produce greater thermal noise currents. Smaller resistors also reduce the sensitivity, so that small input currents are lost in the noise. However, the overall result is that the dynamic range of the transimpedance amplifier circuit is greatly restricted.